It is a conventional practice to perform an inspection for an abnormality in an electrostatic chuck, for example, after such an electrostatic chuck of bipolar type as described above is manufactured, or after the electrostatic chuck is incorporated into an apparatus which uses the electrostatic chuck, such as a semiconductor manufacturing apparatus.
As a method of performing an inspection for an abnormality in an electrostatic chuck, for example, the following method has been conventionally used. That is, by using two ammeters provided between the two attracting electrodes of the electrostatic chuck and the chuck power supply, there are measured leakage currents [steady-state currents after the power supply is turned on (that is, currents which have converged to a constant value)] flowing through both the attracting electrodes under a state in which an object to be attracted such as a substrate is not mounted.
Note that, Patent Literature 1 does not describe a method of performing an inspection for an abnormality in an electrostatic chuck, but describes an example of two ammeters similar to those in the above and current waveforms flowing therethrough. The above-mentioned leakage current corresponds to the steady-state current of the current obtained when a substrate is not placed, which is shown in FIG. 3 of Patent Literature 1.
However, with the conventional inspection method described in Patent Literature 1, it is possible to recognize whether or not there is an insulation failure in galvanic terms, but it is impossible to determine a capacitance abnormality in the electrostatic chuck. Considering that the electrostatic chuck attracts an object to be attracted by means of static electricity, the capacitance abnormality in the electrostatic chuck causes an abnormality in attracting force with respect to the object to be attracted. Further, the capacitance abnormality also causes an adverse effect on a determination of whether or not an object to be attracted exists on the electrostatic chuck, or a determination of whether or not an object to be attracted has been attracted normally. Hence, it is important to detect a capacitance abnormality, instead of an insulation failure in galvanic terms.
In addition, with the inspection method of Patent Literature 1, based on the magnitude of the leakage current, it can be recognized that there is an insulation failure somewhere in the electrostatic chuck, but it is impossible to determine which attracting electrode has an abnormality in its vicinity. For example, it is impossible to determine which one of two attracting electrodes has an abnormality in its vicinity, or to determine whether or not there is an abnormality between the pair of the attracting electrodes. If there is a difference between the measured values of the two ammeters, it may be possible to assume which attracting electrode is closer to the portion of abnormality, but there is no guarantee that the assumption is correct.
Further, apart from Patent Literature 1 described above, there is proposed the following method as a method used in a mounting base for a glass substrate, which includes an electrostatic chuck including chuck electrodes between a lower dielectric body layer and an upper dielectric body layer, and lower electrodes disposed below the electrostatic chuck. In order to diagnose an insulated state of the dielectric body layers before the electrostatic chuck starts to be used, the method includes applying, to the chuck electrode of the electrostatic chuck, a direct current diagnosis voltage which is lower compared to a case where the glass substrate is attracted and held, measuring electric properties (voltage and current) of the electrostatic chuck at this time, and determining whether or not the electrostatic chuck can be used based on the obtained measurement data and preset setting data (Patent Literature 2).
However, similarly to the case of Patent Literature 1, by comparing the measurement data and the setting data, the diagnosis method for the electrostatic chuck described in Patent Literature 2, too, enables determining whether or not there is an insulation failure somewhere in the electrostatic chuck, but it is impossible to determine which attracting electrode has an abnormality in its vicinity.